This invention relates to draw bolts and in particular to such bolts adapted to be locked.
Draw bolt assemblies of the kind to which the invention relates are typically used to lock lorry cargo doors, building doors and in particular external doors or gates. They can also be used to lock windows, vents or cat flaps. Draw bolt assemblies such as those used on external doors and gates generally comprise a housing having a bolt slidably mounted therein, the housing being attached to a surface of the door or gate adjacent the edge which lies opposite the hinge. A receiving member is generally disposed on a door jamb or gate post in such a location that when the door or gate is closed the bolt may be slid along a longitudinal axis of the housing to locate in the receiving member. With such a known system anyone who has access to the draw bolt may lock or unlock the door or gate.
In the past a secure way of locking a draw bolt has been to use a padlock in conjunction with the bolt assembly. However, this can be expensive, and a key is normally required. Additionally, to lock and unlock a padlock is time consuming. This situation can occur for example when a lorry driver is unloading goods and must make several trips, each time leaving the lorry unattended and therefore having to secure the cargo doors each time he is away from the lorry.
The present invention is directed at draw bolt assemblies which are capable of fulfilling broadly the same objectives as those of the prior systems discussed above, but which are capable of being securely locked, and are easier and quicker to use. According to the invention a draw bolt assembly comprises a housing having a passageway formed therein; a bolt slidably mounted in the passageway; and a plurality of annuli aligned in the passageway, each annulus having an internal slot and being restrained by the housing from axial movement relative thereto, the bolt having at least one, and normally a plurality of spigots extending radially therefrom, the spigot or spigots being axially aligned whereby rotation of the annuli to axially align the slots therewith allows movement of the bolt along the passage. Each annulus comprises a body formed with the internal slot and an element bearing a plurality of symbols to be visible on an external surface thereof to indicate the position of the slot in the annulus, the relative orientation of the body and element being adjustable to change the alignment of the slot relative to the symbols. In this way provision is made for altering the sequence of visible symbols that must be established to release the bolt. In other words, the invention provides for a draw bolt assembly to be coded or programmed by the user to require a selected sequence to release the bolt, notwithstanding the sequence installed at the point of manufacture. In some embodiments the housing is attached to a surface using attachment means which are protected from tampering by the annuli and/or the installed bolt.
In preferred embodiments of the invention the body and element of each annulus are themselves annuli in axially abutting engagement, with a locking mechanism setting their relative angular orientation. Typically, the locking mechanism comprises pins extending axially from one of the body and element, and received in at least two of a greater plurality of sockets formed in the other of the body and element. In such an arrangement, the assembly can be dismantled by totally removing the bolt to free the annuli for withdrawal from the housing. The body and element of one or more of the annuli can then be separated, re-oriented and re-coupled, and the annuli then replaced in the housing in a chosen order, which may not be the same as that followed previously, before re-fitting the bolt and completing the re-assembly.
Provision may be made for the re-orientation of the annuli to be accomplished without dismantling the assembly. In other words, it may be made possible to re-code the assembly in situ. More significantly, it enables a purchaser to fit the assembly, and then set a chosen code. A means by which this can be accomplished involves coupling the slotted bodies of the annuli for simultaneous axial movement relative to the symbol-bearing elements. A re-coding key fitted to the assembly can be activated to effect this axial movement of the slotted bodies, normally against some form of resilient mechanism such as a spring. With the bodies and the elements of the annuli disengaged by this movement, they can be relatively re-oriented before being re-engaged with a different selected code or symbol sequence. Such re-coding should only be available to a party knowing the previous code, and thus is preferably only possible while the slots of the annuli are aligned with the spigot or spigots. This is conveniently accomplished by linking or attaching the key to the bolt, and effecting the relative movement of the slotted bodies of the annuli by movement of the bolt beyond its normal locked or unlocked position. A stop mechanism can be provided for normally preventing such abnormal movement of the bolt, but if such movement is possible in any event only when the currently effective code is in place, the mechanism can be no more than a simple screw arrangement, operable without restriction.
The draw bolt assembly of the present invention restricts the movement of the bolt in the housing to movement by a user who knows the selected sequence of symbols that aligns the slots. Assemblies according to the invention are therefore quick and easy to use without the need for a key. Further, the invention allows the selected sequence to be changed easily, for added security.
The bolt of the present invention may also be used as a lockable latch. In this case, a latch member is connected to and biased axially away from the bolt. When the bolt is unlocked, the latch member can move into the housing of the bolt to allow the latch to open and close, but when the bolt is locked, the latch is restrained.